Obtainable in the Tomes of Knowledge Quest. You need to hand these books in to NPC Cael to unlock trading abilities with Farmine NPC's and other rewards. You can only give one Tome of Knowledge to him every 20 hours in real time.

7th Tome: Snake Head Teleport Handing in 7 Tomes you will allow you to use the snake teleport at the peak of the mountain, inside of which Farmine is located. It takes you to the teleporter in northern Zao, south of the Dragonblaze Peaks which is the teleporter to Muggy Plains. The snake head teleport is a one-way teleport only!

8th Tome: Corruption Holes Allows you to enter a hole in the north-eastern end of Zao, where you can find many Lizard Chosen as well as 4 Ghastly Dragon.

10th Tome: Zao Palace Allows you to enter the Zao Palace. It is situated deep underground, below the mountain base of the Lizards. You will find Ghastly Dragons there, but before you get to them you will have to fight your way through hordes of Draken Warmasters and Spellweavers.

More than 12 Tomes: If, by any chance, you are able to get more than 12 Tomes, you can still hand them in to NPC Cael. He will reward you with 5000 experience points for each extra tome you give to him, but still only one is allowed every 20 hours in real time.

Spoiler ends here.

History

Before Update 9.83, Tomes of Knowledge could only be turned in every 24 hours instead of 20.